1. Field of the Invention
The present invention relates to a process for the selective preparation of optionally substituted acetonitriles monohalogenated in the .alpha.-position.
2. Discussion of the Prior Art
It is known to obtain thrichloroacetonitrile by the action of chlorine on acetonitrile in the presence of iodine (Ber.dtsch.chem.Ges. 9, 1594 (1876)). It is further known to react chlorine and acetonitrile at 435.degree. to 440.degree. C. in the vapour phase on a silver-containing catalyst or at 65.degree. C. in the liquid phase whilst irradiating with UV light, to give trichloroacetonitrile (Houben-Weyl, Methoden der organischen Chemie (Methods of Organic Chemistry), Volume V/3, page 634, Georg Thieme Verlag, Stuttgart, 1962). It has also been stated that chlorine in the gas phase does not act on acetonitrile at the boiling point of acetonitrile. The chlorination takes place only above 350.degree. C. (Bull. Soc. Chim. Belges 61, 366 (1952)). It is know to react acetonitrile and chlorine in a ratio of 0.5-0.6:1 in the gas phase at 325.degree. to 380.degree. C. on quartz, active charcoal or perlite to give monochloroacetonitrile in a yield of 75% of the theoretical yield, with conversions of between 90 and 100% (Khim. Prom-st'. (Moscow) 53, 662 (1977)). All of these processes have disadvantages due to the low selectivity and/or the fact that the reactions are carried out at high temperature.